Thanks for the information. As Gabriel Michaud-Verreault said OPC DA protocol is only for real time data only, so in order to back fill either you get the data from the source and back fill using using one of the methods given below or other way is to create one HDA interface instance only for back filling , you need to turn that interface on whenever you want to back fill the data other than keep that instance stopped.

As SaiKumarReddy Pabbathireddy mentioned you can use PI UFL to load data into PI system. If DCS connectivity is failed then PI Buffer will not receive any data from DCS system. Once DCS system is online and if you are using PI HDA interface then you can recover the data for the time period if data is available in your HDA server.

If your OPC Server only supports OPCDA, then you will not be able to recover the data using the OPC Interface since the OPCDA protocol is for real-time data only. If your OPC Server is OPCDA/OPCHDA compliant, then you would need an OPCHDA interface to perform the backfilling.

As others have mentioned, if you have data dumps in ASCII format, then you could use UFL or a programmatic approach (AFSDK, Powershell Tools, piconfig, and many others)

1. If you get the data from the OPC server in excel format, you can either use PI UFL or PI Config or using PI SDK to backfill the data to the PI server.

2. If you want to automatically backfill the data back to PI server, you need to PI OPC HDA interface, so that based on the offset (History availability in OPC server) set in the source side, you can backfill the data. For ex. Yokogawa exaquantum generally have 5 days of offset, so you can backfill the data for the last five days from the communication lost period. If you want to backfill more that period, you need to do it manually (it depends on the OPC server settings).

3. The best to backfill the methods are PI UFL, PI Config or using PI SDK.